微胶囊膜厚的测定及其对释放速率的影响

膜厚是微胶囊重要性能之一,直接影响芯料释放速率,较为难测。本文提出一种测定膜厚的新方法——光学显微镜二次聚焦法,即用光学显微镜二次聚焦直接测出微胶囊内、外径而得膜厚。计算发现微胶囊等光程曲线连续而不光滑(即有拐点),从光学原理上证明此法可行;观察二次聚焦的光学显微图象,发现存在贝克线、从实验结果上间接证明此法可行;此法测定的膜厚与经典法测定的膜厚相比,结果基本一致,证实此法准确。在上述理论基础上,采用相分离法制备一系列不同工艺的微胶囊,分别测出膜厚及芯料释放速率,从而揭示微胶囊膜厚对芯料释放速率的影响规律。

DETERMINATION OF MEMBRANE THICKNESS OF MICROCAPSULES AND ITS INFLUENCE UPON RELEASE VELOCITY

As one of important properties of microcapsule, membrane thickness has direct effects on core material release rate, though there are difficulties for its determination. In this paper a new way, optical microscope double focus method is proposed, that is, to determine membrane thickness through direct testing of interior and outer diameters of microcapsules by optical microscope double focus. Calculation proves that the equal light path curve of microcapsule is continuous but unsmooth.then the applicability of this method is proved by optical principle. Optical microphotos of double focus show the existence of Becke line, applicability of this is also proved by experiment results. Comparisons between membrane thicknesses determined by this method and classical weight method show good similarity, supporting applicability of this way, too. On basis of above mentioned theories, a series of microcapsules made of various techniques are prepared by methods of phase separation. Their membrane thicknesses and release rates are determined so that relations between preparation condition, membrane thickness and release rate are revealed